A nozzle assembly can comprise a nozzle having an outlet, a first inlet, a second inlet, a first circuit from the first inlet to the nozzle outlet, a second circuit from the second inlet to the nozzle outlet, and a fluid-outlet chamber through which both the first circuit and the second circuit pass. Such a two-circuit nozzle assembly can be used, for example, as a fuel injector for a gas turbine engine (e.g., an aircraft engine). In such an application, fuel can be supplied to the first circuit during start-up and low power conditions, and the same or a different fuel can be supplied to both the first circuit and the second circuit during high power conditions. The nozzle can include a set of third circuits through which another fluid is supplied to the fluid-outlet chamber which, in the aircraft engine example, can be air for atomizing purposes.
A nozzle can have a dual-orifice design or a duplex design. In a dual-orifice nozzle, the first circuit and the second circuit have separate swirl chambers, and separate orifices forming the exit from these swirl chambers, upstream of the fluid-outlet chamber. The discharge from a dual-orifice design can have a three-dimensional cone-within-a-cone shape, with the fluid from the first circuit forming the inner cone and the fluid from the second circuit forming the outer cone. (Although sometimes the inner cone and the outer cone intermix and the cone-within-a-cone shape cannot be seen.) In a duplex nozzle, fluid from the first and fluid from the second circuit are intermixed in a common swirl chamber upstream of the fluid-outlet chamber. The intermixed fluids exit from this swirl chamber through a common orifice and are discharged from the nozzle outlet in a single-cone shape.